The present invention relates to an arrangement, for drawing samples or specimens from melts, in which the drawn samples solidify in the absence of air, and in which the gases emitted during cooling and solidification are quantitatively collected.
In the determination of gas content, as well as certain elements of melts that are subject to change due to the influence of air, the drawing of samples or specimens plays a very large role, for two reasons. First, the melt loses certain gaseous constituents during solidification, particularly H.sub.2, CO and in some cases N.sub.2, H.sub.2 O, CH.sub.4 as well.
Secondly, in pouring the melt into an open form, the melt reacts with the oxygen and water vapor in air or on the surface of the form. Since the melts, at their extremely high temperatures, have a high affinity and a rapidity of reaction with the gaseous reagents from the air, uncontrollable errors result.
Swiss Pat. No. 409,469 discloses a procedure for drawing samples that permits the determination of the true gas content of melts, whereby the melt flows into a mold after melting through a replaceable meltable cap, which is sealed by rubber rings to the sample form, and flows through a replaceable metal orifice connected to the sample mold by rubber sealing rings. As soon as the mold is filled and the flow of melt ceases, the melt solidifies in the region of the orifice, producing a hermetic seal against the outside atmosphere. Here the mold has to have such thick walls or has to be constructed of a massive amount of copper to conduct away the heat of the incoming melt, to reach a temperature under 70.degree.C. This is required to prevent the elastic seals between orifice and valve from emitting gas or leaking. Any gases that may have been liberated from the sample during solidification, appear between the sample and the wall, as the solidifying melt contracts. These separated gases can be removed through a valve with an elastic seal, and can be fed to an apparatus for analysis.
The gas remaining in the solidified sample can be exactly determined. After removal of the precision-cast, a highly-polished sample from the mold, a portion of the probe can be subjected to heat extraction. The total gas content of the melt is then the sum of the gas emitted during solidification in the mold and the gas found during heat extraction. The amount of hydrogen emitted in this way during solidification is, on the average, 5 - 30% of the total hydrogen content of the melt.
In scientific investigations of thousands of samples with the above procedure, many exact measurements, demonstrating the laws of movement of hydrogen as well as other gases, could be made. However, it became evident that it would be desirable to improve the above procedure fundamentally in several respects for routine application. With the above procedure, all parts must be cleaned very carefully before each application with particularly pure solvents, particularly CCl.sub.4, because, e.g., the smallest fractions of a mg. of fat, if it came into contact with the liquid melt, could strongly influence the test results. The parts of the mold have to be combined and highly evacuated before each application, with the sealing being accomplished by elastic seals. This presupposes a certain special know-how, since with improper treatment traces of impurities can strongly influence the precision of the results, as described above.
Accordingly, it is an object of the present invention to provide an arrangement for drawing samples, which retains the advantages of the above procedure, namely: drawing of samples and their solidification under seal against air, and the collection of the gases emitted during and after the solidification. But disadvantages from poor cleaning or from overheating of the sample drawing element or its rubber seals are eliminated.
Another object of the present invention is to provide an arrangement of the foregoing character which is simple in design and may be economically fabricated.
A still further object of the present invention is to provide an arrangement, as described, which is reliable in operation and may be readily maintained.